This invention concerns internal combustion engines and more particularly water injection systems for piston engines having air induction systems. There are currently great efforts being exerted to improve the efficiency of operation of internal combustion engines by improving the fuel economy. Such efforts have been made more difficult by the need to maintain certain maximum engine emissions of such pollutants as nitrogen oxide (NOX). Such emissions are produced at relatively elevated engine combustion chamber temperatures.
In an effort to reduce such combustion chamber temperatures, the engine timing has commonly been retarded by manufacturers. While this reduces the combustion chamber temperatures and thus the NOX emissions, it also leads to less efficient engine operation and poorer mileage.
Much of the currently available gasoline fuels are of low octane ratings due to the elimination of lead. Such lower octane ratings result in a tendency for engine knock under heavy load conditions.
This factor also requires relatively retarded engine timing and hence also adversely effects economy of operation.
There is also a tendency for carbon deposits to build up in the engine cylinder on the piston surfaces and spark plugs which increases the tendency for knock and dieseling, and also decreases ignition reliability, all of which adversely affect engine economy.
It has heretofore been known that injection of water in the form of an atomized spray tends to reduce the temperature of combustion within the engine cylinders, reducing the tendency for knock and lowering the temperature levels even at relatively advanced engine timing, such that knocking and the formation of pollutants is reduced.
Overall smoother engine operation results and has a side benefit that the tendency for carbon deposit buildup is reduced, thus tending to alleviate the problems described above and enabling lower octane fuel to be employed as well as the engine timing to be advanced.
However, water injection systems, while long known, have not heretofore found wide application. Water injection, with nonknocking load mixtures, tends to reduce the power output and adversely effect operating economy under these circumstances.
Also, water entering the engine under circumstances has a tendency to produce rusting of the engine components, particularly the carburetor throttle plate, if injection is taking place above the carburetor. Again, entry of water into the engine at relatively low temperatures increases the possibility of icing, hard starting and poor drivability until the engine warms up.
There has heretofore been provided drain means associated with injection apparatus enabling the water to be drained from the system and precluding its seepage into the engine with engine operation ceased. Also, there has heretofore been employed oil pressure switches associates with the injection which precludes the flow of water into the injection system except with the engine in operation.
These measures, however, do not preclude some leakage of water into the engine and also allow water to be injected at relatively low engine operating temperatures. Also, complete draining of the injection system produces an undesirable lag in the initiation of water injection after a cycle or when the engine operation has ceased and water is drained from the system.
It is also highly desirable that such water injection systems, in order to be readily retrofitted, be relatively simple and inexpensive as well as easily installed without major modifications or complicated installation requirements.
Another drawback of such prior art water injection systems is in the relatively large volume of water consumed by the system requiring bulky water tanks or very frequent filling of the reservoir tanks increasing the service requirements associated with vehicle operation.
Accordingly, it is an object of the present invention to provide a water injection system which is highly efficient in operation, achieving a net increase in the operating efficiency of the engine by enabling advance of the engine timing to optimal levels.
It is a further object of the present invention to provide a water injection system which precludes the leakage of water into the engine whenever the engine is not in operation or when the engine is operating cold, i.e., under the normal operating temperature of the engine.
It is another object of the present invention to provide a water injection system in which the water consumption is minimal such as to minimize the need for water reservoir capacity and/or periodic filling.
It is still another object of the present invention to provide such system in which the carbon removal effects of water injection are enhanced such that upon retrofit of such system, the carbon removal progresses at a relatively rapid rate.
It is yet another object of the present invention to provide such arrangement which is relatively simple and low in cost, and adapted to retrofitting to existing nonequipped automobile engines.